As one of printing methods, there is an inkjet method in which an image is formed by ejecting ink droplets from nozzles of an inkjet head to cause the ink droplets to land on a sheet.
Patent Literature 1 describes, among various inkjet methods, a multi-drop method in which multiple ink droplets can be ejected per pixel from one nozzle. In the multi-drop method, gradation printing is performed in which density is expressed depending on the number of ink droplets (drop number) ejected per pixel.